question

hi,
i'm trying to copy UIElement, and it always gives me the same error.
here method i'm trying:

  public static UIElement cloneElement(UIElement orig)
         {
             if (orig == null)
             {
                 return (null);
             }
    
             var s = System.Windows.Markup.XamlWriter.Save(orig);
             var stringReader = new System.IO.StringReader(s);
             var xmlReader = System.Xml.XmlTextReader.Create(stringReader, new System.Xml.XmlReaderSettings());
    
             return (UIElement)System.Windows.Markup.XamlReader.Load(xmlReader);
    
         }

    public static T XamlClone<T>(this T original) where T : class
         {
             if (original == null)
                 return null;
             object clone;
             using (var stream = new MemoryStream())
             {
                 XamlWriter.Save(original, stream);
                 stream.Seek(0, SeekOrigin.Begin);
                 clone = XamlReader.Load(stream);
             }
             if (clone is T)
                 return (T)clone;
             else
                 return null;
         }

here is the error